Pressure ulcers are widely considered to be a critical problem in rehabilitation because they result in severe discomfort and high healthcare costs. The prevention of pressure ulcers is a constant preoccupation for every nursing team as they are a significant secondary complication of mobility impairment. For example, more than 50% of individuals with a spinal cord injury (SCI) will develop a pressure ulcer during their lifetime, and the annual Medicare cost for pressure ulcers in the U.S. is approximately $1.3 billion, which accounts for 25% of the total health care cost for SCI. In addition, other skin diseases (e.g., chronic diseases) have supplanted communicable diseases as the leading cause of morbidity, mortality, and disability worldwide. In particular, venous diseases, such as lipodermatosclerosis, lymphedema, and scleroderma result in complex, non-healing, or recurring wounds accompanied by edema. Such conditions lead to prolonged periods of disability and significantly impact quality of life. Chronic leg wounds, such as pressure ulcers, in the U.S. are estimated to account for the loss of two million workdays a year. Furthermore, the annual cost for the management of these wounds exceeds $20 billion, which excludes the cost of lost workdays and productivity. As the U.S. population ages, the incidence of chronic wounds is expected to rise significantly with projected annual estimates of 5-7 million new cases of chronic wounds.
Early detection of chronic wounds and pressure ulcers is not always a simple matter. The prevalent preventative strategies for detection involve clinical inspection. Clinicians estimate disease stage and progression by feeling or palpating the skin. Palpation methods, however, do not provide an accurate measurement of disease stage and progression, are plagued by inherent subjectivity, and may vary significantly between clinicians, especially those with different levels of skill and experience. Other methods have been explored to objectively assess chronic wound and pressure ulcer risks. For example, a bioimpedance spectrometer was proposed to detect early pressure ulcers. Other approaches used color images to analyze the presence of skin erythema.
The detection of a stage I pressure ulcer is critical because the skin is still intact, and it is easier to recover from this condition. According to the National Pressure Ulcer Advisory Panel (NPUAP), a stage I pressure ulcer is defined as “an observable pressure related alteration of intact skin whose indicators as compared to an adjacent or opposite area on the body may include changes in one or more of the following: skin temperature (warmth or coolness), tissue consistency (firm or boggy feel) and/or sensation (pain, itching).” An important symptom of stage-I pressure ulcer is the change of tissue consistency. Since the skin and subcutaneous tissues start degrading on the early stage of the pressure ulcers, it is likely that the mechanical properties of the skin begin to change simultaneously. Based on past studies, it has been determined that measurement of the mechanical properties of the skin can be used to detect underlying skin diseases. The three main mechanical properties most relevant to clinical determination of pathological conditions are tissue stiffness, viscosity, and skin thickness.
Accordingly, there is a need for systems and methods that objectively measure the changes in the mechanical properties of the skin and the underlying tissue, which would provide an indirect and quantifiable measure of pathological changes in the skin. Much effort has already been dedicated to the development of devices for measuring the mechanical properties of human skin; however, presently available devices are large, expensive, cumbersome, involve complex loading patterns and boundary conditions, and require complex models and heavy data analysis, which are better suited for research studies as opposed to clinical practice. It is to the provision of low cost, handheld systems and methods for the objective, quantitative analysis of the mechanical properties of the skin, which provide a reliable measure across differences in time, environment, and user, that the various embodiments of the present invention are directed.